Add an option to extract more metadata from crawled websites (#4347)

This pr makes it possible to extract more metadata from websites for
later use.

my usecase:
parsing ld+json or microdata from sites and store it as structured data
in the metadata field

langchain/document_loaders/sitemap.py

@@ -11,6 +11,10 @@ def _default_parsing_function(content: Any) -> str:
     return str(content.get_text())
 
 
+def _default_meta_function(meta: dict, _content: Any) -> dict:
+    return {"source": meta["loc"], **meta}
+
+
 def _batch_block(iterable: Iterable, size: int) -> Generator[List[dict], None, None]:
     it = iter(iterable)
     while item := list(itertools.islice(it, size)):
@@ -27,6 +31,7 @@ class SitemapLoader(WebBaseLoader):
         parsing_function: Optional[Callable] = None,
         blocksize: Optional[int] = None,
         blocknum: int = 0,
+        meta_function: Optional[Callable] = None,
     ):
         """Initialize with webpage path and optional filter URLs.
 
@@ -37,6 +42,9 @@ class SitemapLoader(WebBaseLoader):
             parsing_function: Function to parse bs4.Soup output
             blocksize: number of sitemap locations per block
             blocknum: the number of the block that should be loaded - zero indexed
+            meta_function: Function to parse bs4.Soup output for metadata
+                remember when setting this method to also copy metadata["loc"]
+                to metadata["source"] if you are using this field
         """
 
         if blocksize is not None and blocksize < 1:
@@ -56,6 +64,7 @@ class SitemapLoader(WebBaseLoader):
 
         self.filter_urls = filter_urls
         self.parsing_function = parsing_function or _default_parsing_function
+        self.meta_function = meta_function or _default_meta_function
         self.blocksize = blocksize
         self.blocknum = blocknum
 
@@ -110,7 +119,7 @@ class SitemapLoader(WebBaseLoader):
         return [
             Document(
                 page_content=self.parsing_function(results[i]),
-                metadata={**{"source": els[i]["loc"]}, **els[i]},
+                metadata=self.meta_function(els[i], results[i]),
             )
             for i in range(len(results))
         ]

tests/integration_tests/document_loaders/test_sitemap.py

@@ -1,3 +1,5 @@
+from typing import Any
+
 import pytest
 
 from langchain.document_loaders import SitemapLoader
@@ -78,3 +80,45 @@ def test_filter_sitemap() -> None:
     documents = loader.load()
     assert len(documents) == 1
     assert "🦜🔗" in documents[0].page_content
+
+
+def test_sitemap_metadata() -> None:
+    def sitemap_metadata_one(meta: dict, _content: None) -> dict:
+        return {**meta, "mykey": "Super Important Metadata"}
+
+    """Test sitemap loader."""
+    loader = SitemapLoader(
+        "https://langchain.readthedocs.io/sitemap.xml",
+        meta_function=sitemap_metadata_one,
+    )
+    documents = loader.load()
+    assert len(documents) > 1
+    assert "mykey" in documents[0].metadata
+    assert "Super Important Metadata" in documents[0].metadata["mykey"]
+
+
+def test_sitemap_metadata_extraction() -> None:
+    def sitemap_metadata_two(meta: dict, content: Any) -> dict:
+        title = content.find("title")
+        if title:
+            return {**meta, "title": title.get_text()}
+        return meta
+
+    """Test sitemap loader."""
+    loader = SitemapLoader(
+        "https://langchain.readthedocs.io/sitemap.xml",
+        meta_function=sitemap_metadata_two,
+    )
+    documents = loader.load()
+    assert len(documents) > 1
+    assert "title" in documents[0].metadata
+    assert "LangChain" in documents[0].metadata["title"]
+
+
+def test_sitemap_metadata_default() -> None:
+    """Test sitemap loader."""
+    loader = SitemapLoader("https://langchain.readthedocs.io/sitemap.xml")
+    documents = loader.load()
+    assert len(documents) > 1
+    assert "source" in documents[0].metadata
+    assert "loc" in documents[0].metadata